Current methods and devices for recovering oil from mature, low production wells require the withdrawal of large amounts of brine along with the oil. Such methods erode the subsurface oil-bearing reservoirs and result in the well eventually ceasing to produce economic quantities of oil. Also, the brine removed from the well must be disposed of at the expense of the well proprietor.
A number of devices have been introduced which only incidentally purport to recover oil non-continuously from a well, while leaving the brine. So-called oil-only recovery systems are generally not practical for the majority of the well casings which are usually less than 61/2 inches in diameter. Other devices have also been used which are complicated, costly and require format maintenance. These devices are shown in U.S. Pat. Nos. 3,774,685; 4,962,847; 4,962,847; 4,712,667; 1,007,282; 4,542,787; 4,522,220; 4,716,962; 4,683,946; and 4,166,830.